Forums

How to brownout op amp

Started by Henry Parr February 20, 2005
I am designing an Atmel-based circuit with an associated single supply
op amp. I do not want the op amp Iq to deplete batteries any further
than down to about 1V after the programmed micro brownout.

Note that the batteries are not to be manually switched off.

What is the simplest way of doing this?

Thank you,

Henry
Henry Parr wrote:
> I am designing an Atmel-based circuit with an associated single supply > op amp. I do not want the op amp Iq to deplete batteries any further > than down to about 1V after the programmed micro brownout. > > Note that the batteries are not to be manually switched off. > > What is the simplest way of doing this? > > Thank you, > > Henry
Hallo Henry, you could use an OpAmp with shutdown - like TLV2375 from TI. Another possibility is to cut off power from your analog circuitry with a small FET like IRLML6302. Regards Markus
Henry Parr wrote:
> I am designing an Atmel-based circuit with an associated single supply > op amp. I do not want the op amp Iq to deplete batteries any further > than down to about 1V after the programmed micro brownout. > > Note that the batteries are not to be manually switched off. > > What is the simplest way of doing this? > > Thank you, > > Henry
Hi, If its any help here, what I do with PIC's (25 ma for each output) is use them for a power feed for op-amps, eeproms, and other such. No muss, no fuss, just shut down anything drawing less than 25 ma. on their VCC. Also, float or drive low any data lines feeding them. As an example... http://members.cox.net/berniekm/toycar1.gif Here, RB5 is used to power an LM324 and associated circuit. -- Luhan Monat (luhanis 'at' yahoo 'dot' com) "The future is not what it used to be..." http://members.cox.net/berniekm
On Sun, 20 Feb 2005 12:53:13 -0800, the renowned Luhan Monat <x@y.z>
wrote:

>Henry Parr wrote: >> I am designing an Atmel-based circuit with an associated single supply >> op amp. I do not want the op amp Iq to deplete batteries any further >> than down to about 1V after the programmed micro brownout. >> >> Note that the batteries are not to be manually switched off. >> >> What is the simplest way of doing this? >> >> Thank you, >> >> Henry > >Hi, > >If its any help here, what I do with PIC's (25 ma for each output) is >use them for a power feed for op-amps, eeproms, and other such. No >muss, no fuss, just shut down anything drawing less than 25 ma. on their >VCC. Also, float or drive low any data lines feeding them. > >As an example... > >http://members.cox.net/berniekm/toycar1.gif > >Here, RB5 is used to power an LM324 and associated circuit.
If there are external inputs to the op-amp (suppose the op-amp is a CMOS type forming a 1:1 buffer on an input to an ADC, for example) you might want to make sure the input current is limited and/or tristate the output powering the op-amp rather than driving it low. Otherwise you could have a large current flowing from the input, through a protection diode, to the microcontroller output, to ground. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
"Luhan Monat" <x@y.z> wrote in message
news:0V5Sd.77680$Yu.15948@fed1read01...
> Here, RB5 is used to power an LM324 and associated circuit.
Heh - the venerable LM324. You're as much of a dinosaur as I am ;). I *still* specify these in certain cases; it's almost embarrassing... Steve http://www.fivetrees.com
Hello Steve,

>Heh - the venerable LM324. You're as much of a dinosaur as I am ;). I >*still* specify these in certain cases; it's almost embarrassing... > >
So do I. It's not embarrassing but just plain common sense. After all, where can you get a comparable quad opamp where each amp costs less than a nickel? Then, look at stuff that's even older. I can't count how many times I designed in a 2N2907 or its SMT sibling and there is no end in sight.
>http://www.fivetrees.com > >
Hah, we've got six trees here on the lot.... Regards, Joerg http://www.analogconsultants.com
"Joerg" <notthisjoergsch@removethispacbell.net> wrote
> Steve (?) wrote: > >Heh - the venerable LM324. You're as much of a dinosaur as I am ;). I > >*still* specify these in certain cases; it's almost embarrassing... > So do I. It's not embarrassing but just plain common sense.
The LM324 was the most frequent mention in the recent "Name your favorite analog IC's" thread in s.e.d. -- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics.
On Mon, 21 Feb 2005 18:25:19 GMT, the renowned "Nicholas O. Lindan"
<see@sig.com> wrote:

>"Joerg" <notthisjoergsch@removethispacbell.net> wrote >> Steve (?) wrote: >> >Heh - the venerable LM324. You're as much of a dinosaur as I am ;). I >> >*still* specify these in certain cases; it's almost embarrassing... >> So do I. It's not embarrassing but just plain common sense. > >The LM324 was the most frequent mention in the recent "Name your >favorite analog IC's" thread in s.e.d.
Four amplifiers for less than a dime. What's not to like? Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com